The invention relates to a transmission, such as an infinitely variable transmission with wrapped-around conical flanges, with a first pair of conical flanges and a second pair of conical flanges each having an axially movable and an axially fixed flange, and-with a torque transmitting wrapping means disposed between such pairs of conical flanges.
Such transmissions became known, for example, from the published German patent application 195 44 644.
Furthermore, in accordance with the state of art, for example in U.S. Pat. No. 5,649,457, it is known to provide such transmissions with a parking lock wherein a manually operable pawl acts upon a gear which is non-rotatably secured to the shaft of the set of driven flanges. Such arrangement necessitates additional axial installation room on the driven shaft and is expensive.
An object of the present invention is to simplify the construction and the assembly of transmissions of the aforedescribed character and to improve their mode of operation.
In accordance with the invention, this is accomplished in transmissions wherein essentially circular ring-shaped elements form piston/cylinder units and plenum chambers for the application of pressure and/or for axial displacement of the axially movable conical flanges in such a way that at least some ring-shaped elements are connected with a shaft by means of a welded seam.
It might be advisable that the welded seam be provided for the transmission of torque and/or for the prevention of turning.
It is equally of advantage if the welded seam is provided to secure a circular ring-shaped element against axial movement on a shaft.
Furthermore, it is advisable if the welded seam is provided to secure a circular ring-shaped element against axial movement relative to a further ring-shaped element.
In accordance with a further embodiment, it is advisable that the radially inner portions of the circular ring-shaped elements be provided with openings for reception of the shaft and that the welded seam connect the radially inner portions of the circular ring-shaped elements with the shaft.
Furthermore, that object of the invention which involves improving the mode of operation of a transmission of the aforedescribed character is accomplished in that, in order to prevent a rolling away of a motor vehicle which is equipped with the transmission, the latter is provided with a locking device which, when necessary, frictionally locks at least one driving conical flange to a driven conical flange, namely furnishes a means for simultaneous engagement with both conical flanges so that the two conical flanges can no longer turn relative to each other because of the frictional engagement whereby the driven wheels, which are disposed at the end of the power train, can no longer turn relative to each other and, consequently, the vehicle is prevented from rolling away. In such arrangement, no further axial space on the driven shaft is necessary. This renders it possible to dispense with the utilization of an additional toothed gear.
In this connection, it is of great advantage to establish a frictional engagement at the outer peripheries of both conical flanges and to insert a wedge in the gap which develops between the conical flanges in a circumferential direction to thus block the two conical flanges against movement relative to each other. The locking device can be arranged in such a way that a wedge is inserted into the gap from both sides or only from one side. The wedge can be cuneiform or it can conform to the radii of the conical flanges. The material of the wedge can constitute a material with a high friction coefficient, for example, a material for the making of friction linings in clutches of brake linings, or a synthetic plastic material which, if necessary, is reinforced with fibrous filamentary material.
In accordance with the invention, the locking device comprises an actuator which actuates the wedge or wedges, which is preferably provided in the case of the transmission, and which can constitute, for example, an electric motor, a servo cylinder of a hydraulic or pneumatic pressure supplying arrangement, a prestressed spring or a cable winch which latter can be operated mechanically or electrically. In accordance with an inventive concept, an actuator can act upon a wedge or, if two wedges are utilized, an actuator with a suitably designed mechanism can act upon both wedges or a discrete actuator can act upon each of the wedges. An advantage of the utilization of an electrical actuator is that it is not necessary to introduce mechanical or pressurized fluid-conveying lines into the passenger compartment.
Furthermore, it can be of advantage to operate the actuatorxe2x80x94such as a motor, also that of the cable winch or a slave cylinderxe2x80x94during introduction of the wedge or wedges counter to the opposition of an axially compressible energy storing device, for example, a helical-, diaphragm- or coil spring, and to thereupon lock the energy storing device so that, in response to a disengagement, the locking device can be deactivated without it being necessary to employ the actuator. This renders it possible to set up an emergency unlocking function which can release the energy storing device, either mechanically or pyrolytically, so that a disengagement of the locking devices, for example in the event of a malfunctioning of the on-board network or the pressure supplying arrangement, can take place. In the event of a network malfunction, an additionally provided source of electrical energy, such as an accumulator or a battery, can be used to supply energy to an electrically operated actuator. For example, the means for releasing a prestressed energy storing device can consist of or comprise a manually operable cable which can withdraw a bolt of the like from the range of the energy storing device, or a pyrolytic unit which serves the same purpose.
Since at least one conical flange of those conical flanges which are to be locked is movable in the axial direction, and in order to avoid the development of tilting moments of wedges in response to axial displacement of the conical flanges, it is of advantage to provide the outer periphery of at least one conical flange with a circumferential collar which extends in the axial direction to thus ensure that those surfaces of the wedges which abut the conical flanges are disposed at the same level as seen in the axial direction. At the same time, such collar can constitute a constituent of the pressure applying arrangement for the axially movable conical flange and can constitute at least a portion of or a cylinder housing which guides a piston serving as a means for axially stressing the conical flange.
The means for controlling a locking device which is operated by an electrical actuator can include an electric switch which is preferably installed in the passenger compartment so that one can dispense with expensive conductors and mechanical motion transmitting devices.